The present invention relates to devices and methods for protecting the skin and soft tissues at a surgical site, and more specifically surrounding an incision. This invention is particularly useful in conjunction with minimally invasive surgery or minimal incision surgery.
In traditional open surgeries, a large incision is utilized to access the surgical site and provide a wide field of vision. In these types of surgeries, an incision of 7-8 inches is commonplace, as are incisions through the large musculature. Joint replacement surgeries are particularly suited for an open surgery since the surgeon must identify particular bony landmarks, perform osteotomies and properly position and affix the components of a joint endoprosthesis.
However, in recent years, minimally invasive techniques have been adapted to joint replacement surgeries. Minimal incisions are becoming increasingly popular among patients, especially where the surgical scar will be very visible. Moreover, minimally invasive techniques reduce the need to disturb the musculature, which can significantly reduce healing and rehabilitation time following joint replacement.
Notwithstanding the surgical approach, the surgeon must still properly identify bony landmarks that are critical to proper positioning of the joint endoprosthesis. Thus, even when a minimal incision (i.e., an incision less than 7 inches long) is employed, something must be done to allow the surgeon to recognize the appropriate features and properly place the implant relative to those features.
Where the length of the incision limits surgical site visibility, a common practice has been to stretch the incision to thereby increase the area of the opening. The skin and adjacent soft tissues are routinely stretched to their elastic limits. For instance, a 3 inch incision is often stretched to 5-6 inches. Tissue retractors are used to help stretch the incision, as well as to move adjacent soft tissues aside to permit unimpeded viewing of the joint to be replaced. Due to the small incision, and in order to obtain the required exposure, a great deal of leverage or force is applied to the surrounding soft tissues, to stretch the incision using retractors and to elevate the bones of the joint using other instruments.
It has been found that high pressure over long periods of time can lead to necrosis of the skin and the soft tissue surrounding the incision. In tissue tests, a medical pressure sensor (such as an intra-cranial pressure sensor) was placed within a muscle laterally offset from the center of an incision. Pressure measurements are made when retractors are initially positioned within the incision and thereafter as the incision was expanded. It was found that the pressure increased to a magnitude nearly five times greater than the pressure on the wound when the retractors were initially introduced. Thus, with an initial wound pressure of about 20 mmHg, the pressure increased to about 100 mmHg when the incision was fully retracted. This value is within the range of pressures that have been found to produce necrosis in the soft tissues adjacent the incision.
In addition, frictional and shearing forces generated by tools acting against the tissue have been found to contribute to tissue lacerations or necrosis. At a minimum, the pressure exerted on the soft tissues can result in significant discoloration and discomfort to the patient. At the other extreme, the tissue can become necrotic, with the concomitant risk of non-healing and infection. These negative aspects can sometimes negate the benefits of minimal incision or minimally invasive surgical techniques.
As minimally invasive techniques become more prevalent, especially in the field of joint repair and replacement, the need to protect the skin and adjacent soft tissue becomes more acute. Intra-operative wound protection can form a critical prong in an overall wound management program that includes pre-operative treatment, intra-operative and post-operative protocols. Most wound management programs are directed to controlling infection. The major causes of wound infection is by two organisms—Staph Aureus and Staph Epidermidis, skin dwelling organisms that are easily drawn into a wound from the exposed skin by surgical instruments. A pre-incision protocol includes cleaning the skin with a germicide wipe and providing an incision sheet, such as an iodine sheet. A post-operative protocol includes periodically cleaning the wound and applying an anti-infection compound, such as Triclosan, silver ions or chlorhexidine. Post-incision protocols also address non-healing problems, such as by the use of collagen seeds or scaffolds, and pain management issues.
While most of the wound management protocols have focused on pre- and post-incision or operative care, there remains a significant need for wound management during the surgical procedure. Thus, there is a significant need for devices and methods that can protect these tissues during retraction of an incision and throughout the surgery.